1. Field of the Invention
Disclosed herein is a security system for a manhole. The system includes an alarm to indicate that the manhole cover has been removed as well as sensors and alerting means to remotely indicate the presence of a volatile gas within the sewer system in the vicinity of the manhole.
2. Reference to Related Art
Modern cities operate, in part, using a maze of subterranean utility lines, such as water, steam and sewer lines, and underground conduits that may house and protect gas lines, power transmission lines, and a variety of electronic equipment. However, despite the importance of these utilities, the only device that typically stands between a person gaining access to a subterranean line or conduit is a simple iron or steel manhole cover. These manhole covers are quite heavy and, accordingly, might naturally inhibit some attempts at their removal. The actual removal of a cover, however, does not require significant technical expertise. Indeed, at present, it has become common for covers to be stolen simply so the thief may sell the cover for its scrap metal value. Furthermore, while modern covers may create a tight fit around the manhole opening, a cover alone may not create a seal sufficient to prevent fluid from leaking past the cover and into the lines and conduits.
Further the presence of a volatile gas within the manhole can be a serious problem and can lead to explosions causing property destruction and even death.
Accordingly, it would be advantageous to have a manhole security system that may provide an alert following the removal of a manhole cover and/or the presence of a volatile gas within the manhole.